My two cents:
R7 (the RIP only, router) has an interface in the 172.17.0.0 net with a mask
of /24. Whenever any other router advertises a 172.17.0.0 route to R7
(whether another RIP router, or redistributing router), R7 will apply that
24 bit mask to it and insert it into its route table. If the advertised
route doesn't lend itself to the /24 bit mask, R7 will discard it.
That's why this route appeared in R7's table:
R 172.17.2.0 [120/1] via 172.17.10.240, 00:00:09, Ethernet0/0
And all the others were discarded. There was no need for the
summary-address command, it wasn't noticed.
Now, if the IP address numbering scheme were different you would have seen
different results... but you ran the same major network across all the
routers. And contrary to popular belief, RIP (and IGRP) do support
subnets... they just take for granted that you've used the same mask
consistenly throughout the network. If they don't have an interface in the
network at hand, then they go by the major Class. (example: if R7 didn't
have e0/0 in major net 172.17.0.0, then it would have accepted R7's RIP
advertisement and inserted 172.17.0.0 via e0/0 in it's table... and without
the summary-address command).
This is more or less what Bill Dicks was saying, but hopefully it'll be
easier hearing from another perspective.
Gary Frye, Team34 - Network Services
-----Original Message-----
From: Gary Frye [mailto:gfrye@xxxxxxxxxxxxxxx]
Sent: Monday, August 07, 2000 8:58 PM
To: gary.frye@xxxxxxxxxxxxx
Subject: RE: ospf rip redistribution
Phil,
RIP is a FLSM protocol, therefore, in the same major network
(172.17.0.0/16), R2 will only send R7 routes with the same mask as the
interface, which is /24. To get around this you can either re-address the
ospf space to use a different major network so a summary is sent, you can
generate a default and send that, or (the easiest way) is to use rip
verision 2, which supports VLSM.
Bill Dicks
CCIE #6081
-----Original Message-----
From: nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Philip lai
Sent: Monday, August 07, 2000 11:34 AM
To: ccielab@xxxxxxxxxxxxxx
Cc: philip.lai@xxxxxxx
Subject: ospf rip redistribution
ospf rip redistribution
R3--Fr--R2--|--R7
ospf rip
R3 s0.1 172.17.95.1/30
R2 s0.1 172.17.95.2/30
R2 lo 172.17.2.2/24
R2 e0 172.17.10.240/24
R7 eo 172.17.10.241/24
I was trying to redistribute ospf into rip. Since the mask on R2 e0 is
24 bit,
I would like to summarize it before sending into rip.
In R2, I use summary address on ospf.
router ospf 1
summary-address 172.17.0.0 255.255.0.0
network 172.17.95.2 0.0.0.0 area 64
network 172.17.2.2 0.0.0.0 area 64
!
router rip
redistribute ospf 1
passive-interface Serial0.1
network 172.17.0.0
default-metric 1
r2#sh ip route
Gateway of last resort is not set
172.17.0.0/16 is variably subnetted, 5 subnets, 3 masks
C 172.17.10.0/24 is directly connected, Ethernet0
O 172.17.0.0/16 is a summary, 00:09:47, Null0
C 172.17.2.0/24 is directly connected, Loopback0
C 172.17.95.0/30 is directly connected, Serial0.1
O 172.17.95.4/30 [110/128] via 172.17.95.1, 00:03:25, Serial0.1
That was great. A summary address 172.17.0.0/16 was appear. However,
when I
look at routing table of R7. This route do not come out.
r7#sh ip route
C
Gateway of last resort is not set
172.17.0.0/24 is subnetted, 2 subnets
C 172.17.10.0 is directly connected, Ethernet0/0
R 172.17.2.0 [120/1] via 172.17.10.240, 00:00:09, Ethernet0/0
When I try debug ip rip at R2, only 172.17.2.0 are send to R7.
Anybody know what is wrong with the config ? If I need to send a summary
route
to R7. Is that any other way to do it ? Any suggestion are appreciated.
Rdgs,
Philip
r2(config-if)#
00:14:27: RIP: sending v1 update to 255.255.255.255 via Loopback0
(172.17.2.2) -
suppressing null update
00:14:28: RIP: sending v1 update to 255.255.255.255 via Ethernet0
(172.17.10.240)
00:14:28: subnet 172.17.2.0, metric 1
00:14:28: RIP: sending v1 update to 255.255.255.255 via Loopback0
(172.17.2.2)
00:14:28: subnet 172.17.10.0, metric 1
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